Accumulation conveyor

Abstract: An accumulation conveyor (25) includes a plurality of product conveying zones (A,B....N) arranged in tandem, each zone including a series of conveying rollers (30). Each zone includes an actuator (38) for moving a drive belt (40) against the rollers (30) to drive them. Each zone includes a product sensor (42) comprising a mechanical sensor (46) and a valve (62). The valve (62) is pneumatically coupled to the actuator (38) of an upstream zone for causing operation thereof. When a particular one of the actuators (38) is operated, the mechanical sensor (42) positioned in its zone is retracted below the conveying rollers (30).

Description: This invention relates generally to accumulation conveyors such as pneumatically actuated accumulation conveyors. The invention is especially adapted for use with belt-driven roller conveyors utilizing product detecting sensor rollers, but may be used with other drive systems and product detectors. Pneumatically actuated accumulating conveyors have long been known. A commercially successful accumulation conveyor is disclosed in US-A-3768630. The development of accumulation conveyors has evolved to the point where the units are reliable and controlled in a manner to optimize the throughput of product while providing the desired accumulation function. For example, in EP-A-0484098 (see also US-A-5191967, published after the priority date hereof), the drive means of an associated zone is deactivated if the product sensing means for that zone and all of the product sensing means downstream of that zone sense the presence of product in order to produce an accumulation portion in which no zones are actuated. The drive means of an associated zone is actuated if any of the zones downstream of the associated zone are activated in order to produce a transport portion in which all zones upstream of any actuated zone are actuated to transport product without singulation of any upstream grouped product. The drive means for each zone is connected directly to the source of actuating fluid in order to actuate the drive means directly from the source. In WO 93/01113 such direct connection with a source of actuating fluid is accomplished in the same manner by attaching a pneumatic solenoid, or cylinder, to the arm of the sensing roller of the controlled zone and actuating the solenoid from the air diaphragm which actuates the drive means of the zone downstream of the controlled zone. With the pneumatic solenoid operatively positioned to engage the sensor valve for the controlled zone, the precise same operation as set forth in EP-A-0484098 and/or US-A-5191967 is accomplished. When any product sensing roller downstream of a zone does not sense the presence of a product, its sensor valve actuates the air diaphragms in order to drive that zone. This, in turn, actuates the solenoid of the upstream zone which retracts the sensing roller and actuates the sensor valve for that zone which drives the upstream zone. This operation cascades upstream in order to retract the sensor rollers for all zones upstream of a zone that do not sense the presence of product in that zone. While such retractable sensor pneumatic control scheme is a convenient manner to implement the principles of EP-A-0484098 and/or US-A-5191967, it is not without its drawbacks. The mounting of the pneumatic solenoid on the movable arm of the sensor roller is a difficult mounting arrangement, both mechanically and pneumatically, because of the requirement that pneumatic lines be plumbed to a movable member. Furthermore, field retrofit is difficult and time-consuming. An additional difficulty is that packages may have bottom surfaces that are somewhat chamfered or otherwise damaged which creates the possibility that a package in a line of packages accumulating on the accumulation conveyor may not properly actuate a sensing roller. If this occurs, or if a pneumatic solenoid or sensing valve malfunctions, the driving means of all zones upstream of the zone having the malfunction will continue to be actuated resulting in an unacceptable increase in product line pressure. Accumulation conveyors require an extensive inventory of components in order to accommodate various applications. Furthermore, each application must be individually engineered, which requires extensive engineering and drafting time. In addition to the engineering of each conveyor section, the integration of the accumulation conveyor sections with the rest of the conveyor system requires further extensive engineering effort. For example, the location of drive units must be coordinated not only with the rest of the conveyor system but with aisle ways for movement of personnel, lift trucks, and the like. The known accumulation conveyors are not only difficult and time-consuming to engineers, but are also difficult to manufacture. Not only must extensive inventory of components be kept on hand, the assembly of those components requires the application of numerous fasteners, from different directions, which results in excessive assembly time. Furthermore, many of the components are assembled with poor tolerances which must be eliminated by subsequent adjustment of component positioning. This adds yet a further step in the manufacturing process and, hence, to the cost of the unit. It is an object of the present invention to alleviate the difficulties of the prior art and to provide an accumulation conveyor which is economical to engineer and build while being exceptionally functional and reliable in use. According to the present invention there is provided an accumulation conveyor with the features of Claim 1. In a preferred construction, an accumulation conveyor has a pair of spaced-apart support rails, a multiplicity of rollers supported by said rails defining a product conveying surface, an endless drive member juxtaposed with said rollers, a drive motor for driving said drive member, a plurality of product sensors positioned along said conveying surface for detecting the presence of product at positions spaced along said conveying surface and a plurality of actuators positioned along said conveying surface adjacent said drive member for selective reciprocal movement of said drive member into driving engagement with particular rollers adjacent that actuator, each of said actuators having a support member, a contact member that engages the drive member and reciprocates with respect to said support member toward said rollers, and a force producing device between said support member and said contact member, wherein said contact member will respond to said force producing device by bringing the drive member into driving engagement with the rollers adjacent that actuator; each of said product sensors having a sensing member in the path of movement of product on said conveyor and a switching device operated by movement of the sensing member in response to product contacting the associated sensing member; wherein each said switching device is interconnected with the force producing device of an actuator that is upstream of that switching device with respect to movement of product along said accumulation conveyor; and mounting means for selectively mounting each said switching device either to a stationary member, whereby the sensing member is not responsive to actuation of the associated actuator, or to said contact member, whereby actuation of the associated actuator will retract the sensing member from the path of movement of product along said accumulation conveyor. Preferably, said switching device is a valve connected with a fluid source and said force producing device is a fluid-actuated diaphragm. The conveyor may include a fluid manifold mounted to said support member and interconnected with said force producing device and with fluid manifolds of adjacent actuators. Preferably, said stationary member is defined by said support member. Preferably, two adjacent ones of said sensing members are mechanically joined with a connecting member for movement in unison and wherein said connecting member passes through an opening in the support member of at least one of said actuators. Preferably, said support member is mounted to one of said rails. The conveyor may include guide members between said support member and said contact member for guiding said contact member in reciprocal movement with respect to said support member. Preferably, said contact member is a single-piece integral member and defines an elongated low-friction surface engaging said drive member. In another preferred construction, there is provided an accumulation conveyor having a pair of spaced-apart support rails, a multiplicity of rollers supported by said rails, an endless drive member juxtaposed with said rollers, a drive motor for driving said drive member, a plurality of product sensors positioned along said conveyor for detecting the presence of product at positions spaced along said conveyor and a plurality of control devices positioned along said conveyor, each for selective reciprocal movement with respect to particular rollers adjacent that control device, each said control device comprising: a support member mounted to one of said rails and including means defining a cavity therein; a force-producing member in said cavity; a contact member between said force-producing member and the rollers adjacent that control device wherein operation of said force-producing member will move that contact member toward said rollers adjacent that control device; guide members between said belt-contacting member and said support member to guide reciprocal motion of said belt-contacting member with respect to said support member; and a signal manifold mounted to said support member and interconnected with said force-producing device and with fluid manifolds of adjacent control devices in order to coordinate said control devices. The conveyor may include a low-friction surface on said contact member of particular ones of said control devices that are juxtaposed with the drive member in order to selectively bring the drive member into driving engagement with the rollers adjacent said particular ones of said control devices. Alternatively or additionally, the conveyor may include a high-friction surface on said contact member of particular ones of said control devices that are not juxtaposed with said drive member in order to selectively brake the rollers adjacent said particular ones of said control devices. Preferably, the conveyor includes a plurality of product sensors, wherein each of said product sensors include a sensing member in the path of movement of product on said conveyor and a switching device operated by movement of the sensing member in response to product contacting the associated sensing member, and wherein said switching device is mounted to one of said control devices between the support member and contact member of that control device and is interconnected with the signal manifold of that control device. Preferably, said force-producing member is a fluid-actuated diaphragm and said switching device is a fluid valve connected with a source of fluid. Each said fluid valve may be interconnected through the fluid manifold with the diaphragm of at least one control device upstream thereof with respect to product movement along said conveyor. Preferably, two adjacent ones of said sensing members are mechanically joined with a connecting member for movement in unison and wherein said connecting member passes through an opening in the support member of at least one of said control devices. In another preferred construction, there is provided an accumulation conveyor having a pair of spaced-apart support rails, a multiplicity of rollers supported by said rails defining a product conveying surface, an endless drive member juxtaposed with said rollers, a drive assembly for driving said drive member, a plurality of product sensors positioned along said conveyor for detecting the presence of product at positions spaced along said conveying surface and a plurality of actuators positioned along said conveying surface adjacent said drive member for selective reciprocal movement of said drive member into driving engagement with particular rollers adjacent that actuator, said drive assembly being substantially entirely supported by said pair of spaced-apart support rails wherein said drive assembly may be at substantially any longitudinal position with respect to said product conveying surface. Preferably, said drive assembly includes a rectangular frame having a pair of opposite side members joined with said pair of space apart support rails. Preferably, said drive assembly includes a drive motor assembly and a take-up assembly, said drive motor assembly having a drive sheave for driving said endless drive member and said take-up assembly having a take-up sheave for removing slack from said endless drive member and means for applying a bias to said take-up sheave and wherein said take-up sheave is reciprocatingly mounted to one of said side members by a reciprocating mounting device. Preferably, said reciprocating mounting device includes a pair of ball slides. In another preferred construction, there is provided an accumulation conveyor having a pair of spaced-apart support rails, a multiplicity of rollers supported by said rails defining a product conveying surface, an endless drive member juxtaposed with said rollers, a drive motor for driving said drive member, a plurality of product sensors positioned along said conveyor for detecting the presence of product at positions spaced along said conveying surface and a plurality of actuators positioned along said conveying surface adjacent said drive member for selective reciprocal movement of said drive member into driving engagement with particular rollers adjacent that actuator, at least one discharge roller at a discharge end of said conveying surface to discharge product from said conveying surface; a return sheave for the endless drive member juxtaposed with said at least one discharge roller, said return sheave mounted for reciprocal movement toward said at least one discharge roller; and control means for selectively moving said return sheave toward said at least one discharge roller to thereby bring said endless drive member into driving engagement with said at least one discharge roller to discharge product from said conveying surface. Preferably, said return sheave is mounted by an eccentric and said control means includes means for rotating said eccentric. Preferably, said control means includes a fluid-actuated cylinder. Preferably, said at least one discharge roller includes more than one adjacent roller joined by coupling means for providing joint rotation of said adjacent rollers. The conveyor preferably includes a brake member for selectively braking said at least one discharge roller when said control means is not moving said return sheave toward said at least one discharge roller. In another preferred construction, there is provided an accumulation conveyor having a pair of spaced-apart support rails, a multiplicity of rollers supported by said rails defining a product conveying surface, an endless drive member juxtaposed with said rollers, a drive motor for driving said drive member, a plurality of product sensors positioned along said conveying surface for detecting the presence of product at positions spaced along said conveying surface and a plurality of actuators positioned along said conveying surface adjacent said drive member for selective reciprocal movement of said drive member into driving engagement with particular rollers adjacent that actuator, each of said product sensors having an elongated sensing member selectively in the path of movement of product on said conveyor and a counterweight, the difference in weight between said counterweight and said sensing member biases said sensing member upwardly into said path of movement of product; and said counterweight including at least one weight member and an elongated spacer, said spacer approximately the same weight as said sensing member whereby said difference in weight is established by said weight member. Preferably, said weight member is a pair of members separated by said spacer. Preferably, said spacer member has approximately the same weight per unit length as said sensing member. Preferably, said spacer is non-rotatably mounted. According to a further aspect of the invention there is provided a method of selectively conveying and accumulating product including: providing a plurality of product conveyors arranged in tandem and each including a product conveying surface; providing retractable product sensors along said product conveying surfaces for sensing the presence of product when not retracted; providing actuators for causing each of said product conveyors conveying surfaces to convey product; causing motion in one of said actuators to actuate the associated product conveyor and thereby convey product with said associated conveying surface; characterised by mechanically coupling the actuator for a particular conveyor to a said product sensor which is located at the particular conveyor, the said motion of the actuator for the particular conveyor, in response to another downstream product sensor, retracting the coupled product sensor from the path of movement of product along the accumulation conveyor concurrently with actuation of said particular one of said product conveyors. The method preferably includes positioning said other one of said product sensors juxtaposed with said one of said actuators. The method preferably includes attaching a portion of said other one of said product sensors to said one of said actuators. Preferably, said providing product sensors includes providing sensing members responsive to the presence of product and switching members selectively actuatable by said sensing members. The method preferably includes, mounting said switching member of said other one of said product sensors to said one of said actuators. In another preferred construction, a multiple mode accumulation conveyor has an anti-singulation control capable of deactivating the drive means of a zone if the product sensing means for that zone and substantially all of the product sensing means downstream of that zone sense the presence of product in order to produce an accumulation portion in which no zones are actuated. The control is further capable of activating the drive means of a zone if any of the drive means downstream of the associated zone are actuated in order to produce a transport portion in which all zones upstream of any actuated drive means are actuated to transport product without singulation of any upstream grouped product. In another preferred construction, each of the product sensors includes an arm that is selectively positioned in the path of product being conveyed by the product conveyors, a switch having an actuation member juxtaposed with the arm and a force-producing connection from an actuator of a downstream zone, in order to move the arm from a position in the path of product being conveyed to a retracted position. The force-producing connection includes the switch being positioned in a line of force between the downstream zone actuator and the arm whereby product on the accumulation conveyor causes the arm to actuate the switch when the arm is positioned in the path of product being conveyed. The force-producing connection may include a solenoid, or cylinder, or mechanical linkage, that is responsive to actuation of the downstream zone actuator in order to apply a force to the switch. The solenoid and switch may both be mounted to the frame thus freeing the arm of any plumbed attachments. Additionally, the switch and solenoid may be combined in a unitary package that is readily adaptable to field upgrade of existing accumulation conveyors. In another preferred construction, a product sensor is positioned along an accumulation conveyor at a particular conveyor zone for sensing the presence of product at that zone and for causing actuation of a zone upstream of that product sensor with respect to product movement along the accumulation conveyor. An actuator is provided for that particular zone that is mechanically coupled with the product sensor physically located in that zone. When the actuator is actuated to power that zone, it retracts the product sensor from the path of movement of product along the accumulation conveyor, concurrently with actuation of that zone. In this manner, a retractable sensor function may be achieved without the requirement for a separate solenoid or pneumatic cylinder. This is accomplished by utilizing the mechanical movement of the actuator of the zone in which each product sensor is physically located in order to effect the retraction. This provides an enormous savings in component count and, hence, cost. In a preferred embodiment, each of the product sensors may have a sensing member in the path of movement of a product and a switching device, such as a fluid valve, operated by movement of the sensing member in response to product contacting the associated sensing member. Each of the actuators may have a support member, a contact member that engages an endless drive member and reciprocates with respect to the support member toward the rollers. The actuator further includes a force producing device, such as a diaphragm, between the support member and contact member. The switching device may be mounted with one of the actuators and is interconnected with the force producing member of an actuator that is upstream thereof with respect to movement of product along the accumulation conveyor. The switching device may be selectively mounted either to a stationary member, such as the support member, or to the contact member. If the switching device is mounted to a stationary member, the sensing member is not responsive to actuation of the associated actuator and a non-retractable sensor function is achieved. If the switching device is mounted to the contact member, actuation of the associated actuator will retract the sensing member from the path of movement of product along the accumulation conveyor. Thus, two widely disparate functions are achieved with precisely the same hardware assembled in a slightly different manner. In another preferred construction, an accumulation conveyor includes a pair of spaced-apart support rails, a multiplicity of rollers supported by the rails, an endless drive member juxtaposed with the rollers, and a drive motor for driving the drive member. A plurality of product sensors are positioned along the conveyor for detecting the presence of product at positions spaced along the conveyor. A plurality of control devices are positioned along the conveyor, each for selective reciprocal movement with respect to particular rollers adjacent that control device. Such control device may include a support member that is mounted to one of the rails and defines a cavity therein in which a force-producing device is located. A contact member is positioned between the force-producing device and rollers, and reciprocates with respect to the support member. A signal manifold is mounted to the support member and interconnects with the force-producing device and with signal manifolds of adjacent control devices. By providing a low-friction surface on the contact member, the control device may be juxtaposed with the drive member to serve as an actuator to selectively bring the drive member into driving engagement with the rollers adjacent that control device. By providing a high-friction surface on the contact member and not juxtaposing that member with the drive member, a brake device is provided to brake the rollers adjacent to that control device. Again, two widely disparate functions are achieved with hardware having a great number of common components. In a preferred embodiment, a discharge roller is provided at a discharge end of the accumulating conveyor that is selectively operable to discharge product from the conveyor. According to this aspect, a return sheave is provided for the endless drive member, below the discharge roller, in a manner that the return sheave is capable of vertical reciprocal movement, and a control is provided for selectively moving the return sheave toward the discharge roller when it is desired to discharge product from the conveyor. This selectively brings the drive member into driving engagement with the discharge roller in order to discharge product from the conveying surface. Preferably, a drive assembly is provided for driving the endless drive member. The drive assembly is entirely supported by the side rails of the accumulation conveyor. This allows the drive assembly to be positioned at substantially any longitudinal location along the product conveying surface. In a preferred form, the drive assembly includes a drive motor assembly and take-up assembly. The drive motor assembly has a drive sheave for driving the endless drive member. The take-up assembly has a take-up sheave for removing slack from the endless drive member and means for applying a bias to the take-up sheave. The take-up sheave is reciprocally mounted to one of the side members of the rectangular frame of the drive assembly by a reciprocating mounting device. In a most preferred form, the reciprocating mounting device is a pair of ball slides. Preferably, each of the product sensors includes an elongated sensing member and a counterweight. The difference in weight between the counterweight and the sensing member biases the sensing member upwardly into the path of movement of product on the conveyor. The counterweight includes at least one weight member and an elongated spacer. The spacer is approximately the same weight as the sensing member. Therefore, the difference in weight biasing the sensing member upwardly is established by the weight member. In this manner, the same component configuration can be applied to any width conveyor because the bias force is independent of the actual weights of the product sensors and spacers, which will vary with conveyor width but will be essentially equal. Preferred embodiments allow maximum use of automated equipment to assemble accumulation conveyors by significantly reducing the number of fasteners, by assembling components from a uniform direction and by eliminating common alignment procedures. The number of components may be greatly reduced and, hence, design is simplified and inventory carrying costs are reduced. This may be accomplished by utilizing common component designs for various functions and by performing control functions using non-traditional techniques. Not only are the engineering effort and assembly activities at the factory reduced greatly, but also the design effort required at the site. This may be accomplished, by way of example, by providing drive units that may be positioned at substantially any location along the accumulation conveyor. In addition to providing an economical accumulation conveyor that is exceptionally durable and reliable in use, the preferred embodiment provides exceptional control over product on the accumulation conveyor, for example, by dividing the conveying surface longitudinally into a greater number of short control zones. The present invention may be carried out in various ways and various embodiments of accumulation conveyors in accordance with the invention will now be described, by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectioned side elevation illustrating a portion of an accumulation conveyor which does not form part of the invention; Fig. 2 is an enlarged side elevation of a product sensor for the conveyor of Fig.1; Fig. 3 is the same view as Fig. 2 in a different control state; Fig. 4 is the same as Fig. 2 except in yet a different control state; Fig. 5 is a pneumatic schematic diagram of an accumulation conveyor bed which does not form part of the invention; Fig. 6 is a perspective view of a segment of an alternative accumulation conveyor according to a preferred embodiment of the invention; Fig. 7 is a side elevation of the accumulation conveyor segment in Fig. 6; Fig. 8 is an end elevation of the accumulation conveyor segment in Fig. 6; Fig. 9 is a top plan view of the accumulation conveyor segment in Fig. 6; Fig. 10 is an exploded perspective view of the accumulation conveyor segment in Fig. 6; Fig. 11 is an exploded perspective view of a portion of an alternative embodiment of the accumulation conveyor segment in Fig. 6 illustrating a preferred pneumatic interconnection of adjacent actuators; Fig. 12 is a perspective view of a preferred actuator assembly and juxtaposed retractable sensing roller; Fig. 13 is the same view as Fig. 12 of a preferred additional actuator assembly that is configured to not retract the sensing roller; Fig. 14 is a sectional view taken along the lines XIV-XIV in Fig. 12; Fig. 15 is a sectional view taken along the lines XV-XV in Fig. 13; Fig. 16A is a schematic diagram of a pneumatic control system according to a preferred embodiment of the invention; Fig. 16B is a schematic diagram of an alternative pneumatic control system; Fig. 17 is a side elevation illustrating an actuator and retractable sensing roller with the sensing roller in an extended position; Fig. 18 is the same view as Fig. 17 with the sensing roller detecting the presence of a product; Fig. 19 is the same view as Fig. 17 with the retractable sensing roller retracted by actuation of the actuator; Fig. 20 is a perspective view of a brake control device according to a preferred embodiment of the invention; Fig. 21 is a side elevation of a preferred discharge portion of an accumulation conveyor in a non-discharge mode; Fig. 22 is the same view as Fig. 21 with the accumulation conveyor in a discharge mode; Fig. 23 is a perspective view of a drive assembly according to a preferred embodiment of the invention; Fig. 24 is a side elevation of a drive assembly positioned at the intake end of the accumulation conveyor; Fig. 25 is the same view as Fig. 24 of a drive assembly positioned anywhere between the intake end and the discharge end of an accumulation conveyor; Fig. 26 is a perspective view of another alternative embodiment of an accumulation conveyor according to another preferred embodiment of the invention having interconnected adjacent sensing rollers; Fig. 27 is an end elevation of the embodiment in Fig. 26; Fig. 28 is a side elevation of an alternative embodiment of the sensing roller configuration useful with a preferred embodiment of the invention in an extended position; and Fig. 29 is the same view as Fig. 28 illustrating the sensing roller detecting the presence of a product. Referring now specifically to the drawings and the illustrative embodiments depicted herein, an accumulation conveyor 1 shown in Figure 1, which does not form part of the invention, includes a frame 2 supporting a multiplicity of rotatable rollers 3 and a plurality of drive means 4, such as continuously rotatable chains, belts, bands or other such means, that are actuatable by actuation means, such as pneumatic air bags 5, in order to power rollers 3 to convey product, such as packages 6, from left-to-right, as viewed in Fig. 1. Rollers 3 are divided into zones, each zone driven by a particular drive 4. The air bags, or actuation means, for each drive are actuated from a source of compressed air 7 through a pneumatic control 8. Pneumatic control 8 is responsive, in part, to a product sensor 9 positioned immediately downstream, with respect to product flow, of the rollers making up the zone that is controlled by that product sensor so that the rollers making up the zone controlled by a particular pneumatic control 8 are positioned upstream of that control. As will be set forth in more detail below, in most zones, pneumatic control 8 for each actuation means 5 is additionally responsive to the actuation means immediately downstream of that zone. In this manner, each such interdependent pneumatic control is responsive to actuation of the drive downstream of the associated zone in order to actuate the drive of the associated zone if any of the drives downstream of the associated zone are actuated. This produces a transport portion of accumulation conveyor 1 in which all drives upstream of any driven zone are actuated in order to transport product without singulation of any upstream grouped products. The pneumatic control 8 deactivates the drive of its associated zone if product sensor 9 for that zone senses the presence of product and all of the drives downstream of that zone are deactivated. This produces an accumulation portion in which no drives are being actuated. In this manner, an interface between zones that are in the accumulation portion and zones that are in the transport portion is dynamically shifting in response to product movement along the accumulation conveyor 1 in order to provide product accumulation without singulation of groups of upstream product, as is set forth in more detail in EP-A-0484098 and/or US-A-5191967. Each product sensor 9 includes an actuator arm 10 that is pivoted at 11 in order to move a sensing roller 12, that is rotatably mounted on actuator arm 10, between a product sensing position, as illustrated in Fig. 2, and a retracted position, as illustrated in Fig. 3. A spring 13 affixed at one end to frame 2 biases actuator arm 10 into a product sensing position. Product sensor 9 additionally includes a pneumatic control module 8 composed of a pneumatic solenoid, or cylinder, 14, and a valve 15 commonly mounted to a flanged bracket 16. Solenoid 14 is fixedly mounted to bracket 16 which is, in turn, fixedly mounted to frame 2. Valve 15 is mounted to a movable member 14 of solenoid 14, which extends in response to actuation of solenoid 14. In particular, with solenoid 14 deactuated, valve 15 is in the position illustrated in Figs. 2 and 4 abutting the upstanding flange portion of bracket 16. When solenoid 14 is actuated, valve 15 is reciprocated away from bracket 16 as illustrated in Fig. 3. Valve 15 includes an actuator 17 which engages an extension portion 18 of actuator arm 10. As may be seen by comparing Figs. 2, 3 and 4, solenoid 14 is actuatable in order to produce a force responsive to actuation of the zone downstream of the zone controlled by the pneumatic control 8 incorporating that solenoid 14. Solenoid 14 produces such force in order to retract sensing roller 12 from the sensing position illustrated in Fig. 2 to the retracted position illustrated in Fig. 3. When the solenoid 14 is deactuated and no product is engaging sensor roller 12, valve 15 is being actuated by the force of spring 13 upon actuator arm 10. In such extended sensing position, product sensor 9 will respond to the presence of a package 6 by deactuating valve 15, as seen in Fig. 4. When solenoid 14 is actuated, as seen in Fig. 3, actuator arm 10 is pivoted to a retracted position by way of the movement of valve 15 under the force exerted by solenoid 14. Because valve 15 is thrust against actuator arm 10 in order to pivot the arm, valve 15 is concurrently actuated in the sensor retracted position illustrated in Fig. 3. Although the force-producing connection from the actuator 5 of the downstream zone in order to retract sensing roller 12 is illustrated as a pneumatic solenoid, other connections are possible. Alternatives may include an electrically actuated solenoid or a mechanical linkage. Product sensors 9 are organized in a conveyor bed 19 into interdependent sensors 20 and guardian sensors 21. Each interdependent sensor 20 includes a first input 22 connected directly with source of compressed air 7 and a second input 23 connected with a line 24, which is outputted from the downstream product sensor 9. Line 24 extends from a product sensor 9 to the actuating means 5 of the zone associated with that product sensor. Line 24 is selectively pressurized by valve 15 in order to actuate the actuator means 5 of the downstream zone and causes the associated drive to rotate the rollers in the downstream zone. Valve 15 is pneumatically in series between input 22 and line 24 in order to interconnect the two lines when the valve is being actuated by depressing its actuator 17. Valve 15 interconnects line 24 with atmosphere when valve 15 is not actuated. The actuation port of solenoid 14 for each interdependent product sensor 20 is pneumatically connected to receive the second input 23 for that sensor. In this manner, solenoid 14 associated with each interdependent sensor 20, is actuated whenever the actuating means of the zone downstream of that controlled by that sensor 20 is actuated. Because the actuation of solenoid 14 results in actuation of valve 15 on its product sensor, as seen in Fig. 3, the pneumatic control 8 associated with a particular zone will actuate the drive of that zone if the downstream zone is being actuated. Because each such zone is, in turn, interdependent on the zone downstream of it, any interdependent sensor 20, which does not sense the presence of product in its zone, will cause all contiguous upstream zones thereof controlled by interdependent sensors 20 to be actuated. An accumulation conveyor 25 shown in the embodiment of Figure 6 includes a pair of side rails 26, 26' joined by a cross member 28 at longitudinally spaced intervals. A multiplicity of rotatably mounted rollers 30 extend between side rails 26, 26' along the entire length of accumulation conveyor 25 in order to define a conveying surface. The rollers are mounted to openings 32 formed in side rails 26, with a noise-reducing isolation strip 33 optionally provided between the rollers and side rails. If rollers 30 are spaced sufficiently far apart, such as on 76.2 mm (three-inch) centers, finger guards 34 may be provided between adjacent rollers in order to provide protection against a user engaging the moving components of the accumulation conveyor. In the illustrative embodiment of Fig. 6, accumulation conveyor 25 is divided into a plurality of zones "A", "B", "C" . . . "N", (only zone "A" and zone "B" being illustrated in Fig. 6), each zone capable of being actuated separately from the other zones. An endless drive member, such as drive belt 36, provides the mechanical force for driving rollers 30 for all of the zones. Each zone includes at least one control device, such as an actuator 38, 38', juxtaposed with the upper portion 40 of drive belt 36 beneath rollers 30. Each actuator 38, 38' is adapted to bringing upper portion 40 of drive belt 36 into driving engagement with the rollers 30 immediately above that actuator. A product sensor 42 is provided for each zone in order to operatively control the actuator(s) 38, 38' for that zone. Product sensors 42 are physically located in a zone downstream of the zone that is operatively controlled by the product sensor, with respect to product flow. Using Fig. 16A as an example, the product sensor 42 controlling zone "A" is positioned in zone "B" above the actuator 38 for zone "B". Product sensor 42 includes a pair of sensor arms 44, which are joined by a sensing roller 46 and a counterweight 48. Product sensor 42 is mounted to pivot about a roller 30. To this end, each sensor arm 44 includes an opening 50 and a sleeve 51, which receives the shaft 52 of the roller 30 to which the product sensor 42 is pivotally mounted. Counterweight 48 includes a spacer shaft 54 that, in the illustrated embodiment, is non-rotatably mounted by a pair of weights 56. Because the weights of sensing roller 46 and spacer are proportional to the width of accumulation conveyor 25 and are made equal, weights 56 may be selected to provide the desired net bias force on sensing roller 46 irrespective of the width of conveyor 25. Weights 56 are selected to bias sensing roller 46 upward into the path of product moving along accumulation conveyor 25. Product sensor 42 additionally includes a lever 58 extending from each sensor arm 44 for the purpose of interconnecting adjacent product sensors 42, when it is desired to provide an enhanced sensing area, as is known in the art. Product sensor 42 additionally includes an actuating surface 60 defined on one of the sensor arms 44 for the purpose of interaction with a pneumatic valve 62 in a manner that will be set forth in more detail below. Actuator 38 includes a support member 64 which is mounted to a side rail 26 by integrally formed hook and snap fasteners 66, only two of which can be seen in Fig. 10. Fasteners 66 engage four (4) openings 68 formed in side rail 26. Support member 64 includes a horizontal surface 70 having a cavity 72 defined therein. Cavity 72 is configured to retainably receive a conventional fluid-actuated diaphragm, or pneumatic actuator, 74 of the type well known in the industry. Support member 64 further includes a pair of guide members 76 to provide movable support for a contact member 78 to selectively reciprocate vertically with respect to support member 64. Contact member 78 includes a low-friction slider surface 80 and integral belt guides 82 in order to interface with upper portion 40 of drive belt 36. With diaphragm 74 positioned between support member 64 and contact member 78, application of compressed air to diaphragm 74 will reciprocate contact member 78 upwardly in order to bring upper portion 40 of drive belt 36 into driving engagement with the rollers 30 adjacent actuator 38. Actuator 38 additionally includes a pneumatic block 84, 84' with input ports 86 and output ports 88 that are interconnected with adjacent actuators 38 by ribbon tubing 90 (Figs. 11 and 16B). Pneumatic block 84, 84' additionally includes interconnect ports 92 for direct engagement with valve 62 and diaphragm 74 associated with actuator 38. Pneumatic block 84, 84' further includes a pair of clips 94 for snap retention with recesses 96 defined in support member 64. Valve 62 is positioned in a cavity 98 defined between a vertical wall 100 of support member 64 and a vertical member 102 of contact member 78 (Figs. 12-15). When valve 62 is so positioned in cavity 98, its actuator 104 is in actuating engagement with actuating surface 60. Valve 62 includes a mounting flange 106. Each of vertical wall 100 and vertical member 102 are configured within cavity 98 to capture mounting flange 106 and, thereby, fixedly mount valve 62 thereto. Figs. 13 and 15 illustrate valve 62 mounted to vertical wall 100. In this configuration, illustrated in Figs. 13 and 15, actuating surface 60 of product sensor 42 operates actuator 104, under the bias of counterweight 48, when product sensor 42 is not sensing the presence of product in the vicinity of product sensor 42. When product comes into contact with sensor roller 46, the movement of sensor arm 44 disengages ctuating surface 60 from actuator 104 which allows actuator 104 to extend to a non-actuated position under the influence of the air pressure within the valve and an optional internal spring (not shown) in valve 62. In such non-actuated extended position, valve 62 is normally closed to prevent flow from an input line 108 to an output line 110 of the valve. Conversely, when actuating surface 60 biases actuator 104 downwardly under the bias of counterweight 48, in the absence of sensing roller 46 being contacted by a product, valve 62 is actuated into an open-fluid conveying configuration between input 108 and output 110. In the embodiment illustrated in Figs. 13 and 15, valve 62 is fixedly mounted to stationary vertical wall 100 of support member 64 and completely separated from vertical member 102. Thus, vertical movement of contact member 78 has no effect on valve 62 positioned within cavity 98 nor on product sensor 42 that actuates valve 62. In the configuration, as illustrated in Figs. 13 and 15, sensing roller 46 is biased upwardly into a product sensing position and is deflected downwardly only in response to contact by a product on the conveying surface. In the embodiment illustrated in Figs. 12 and 14, flange 106 of valve 62 is fixedly mounted to vertical member 102 of contact member 78. Otherwise, the interface between valve 62 and product sensor 42 is the same. Actuating surface 60 directly contacts with actuator 104. However, in the configuration illustrated in Figs. 12 and 14, contact member 78 moves upwardly in response to the inflation of diaphragm 74 associated with contact member 78. This movement lifts valve 62 upwardly concurrently with movement of the contact member. The upward movement of valve 62 applies an upward force on actuating surface 60, which rotates product sensor 42 about shaft 52 in a manner that retracts sensing roller 46 downwardly out of the path of movement of product along the conveying surface, irrespective of whether product is engaging the sensing roller. As best illustrated in Figs. 16A and 16B, each valve 62 and its operatively associated product sensor 42 may be positioned physically in the zone operated by the actuator within whose cavity 98 valve 62 is positioned. Each zone may be the length of a single actuator 38, as illustrated in Fig. 16A, or may be the length of multiple actuators 38, 38', as illustrated in Fig. 16B. Valve 62, in turn, is pneumatically operatively interconnected with diaphragm(s) 74 of a zone upstream to that in which the valve and product sensor are positioned, with respect to movement of product along the accumulation conveyor. The zone to which valve 62 is operatively interconnected may be, but is not necessarily, the adjacent upstream zone. Thus, for example, with valve 62 mounted to vertical member 102 of contact member 78, as illustrated in Figs. 17 and 19, the sensing roller 46 for zone "B" is biased into the path of movement of product along the conveying surface, as illustrated in Fig. 17, when the actuator 38 of zone "C" mounting the valve is actuated, as illustrated in Fig. 18. If a product then actuates the sensor of zone "B", it will extend the sensing roller 46 for zone "A" into the path of movement of product and so on in a succession. If the actuator 104 of the valve 62 for zone "B" located in zone "C" is biased into an open position, as illustrated in Fig. 18, the diaphragm in the upstream zone "B" is actuated by bringing the upper portion 40 of the drive belt into driving engagement with the rollers 30 of that upstream zone "B" which, in turn, retracts the sensor 42 for zone "A" located in zone "B". A product "X" moving along the conveying surface into zone "C" will deflect product sensor 42 (Fig. 18). This will move contact surface 60 away from valve 62 allowing actuator 104 to extend upwardly, closing valve 62. This deactuates the upstream zone "B" operatively controlled by valve 62 to place that upstream zone "B" in an accumulation mode similar to that in Fig. 18. If actuator 38 of zone "C" is actuated into a conveying mode, as illustrated in Fig. 19, the upward reciprocation of contact member 78 will retract sensing roller 46 for zone "B" from a product detecting position with the path of product movement of the conveyor. Because the retraction of sensing roller 46 is a result of valve 62 providing an upward force against actuating surface 60, the retraction of sensing roller 46 additionally actuates valve 62 into an open state which inflates the diaphragm of its operatively associated zone "A" in order to place that upstream also into a conveying mode. Operation of such a control scheme is otherwise the same as that of accumulation conveyor 1. Such control scheme produces a conveying portion of accumulation conveyor 25 in which all of the upstream zones of any zone whose operatively connected product sensor 42 does not sense the presence of product, are actuated and the sensors physically located in the conveying portion are retracted. Only a sensor physically located in a zone in an accumulation mode, in which the actuator is not applying the drive belt to the rollers above it, will be extendable into a sensing position with respect to product along the conveyor. Importantly, this function is achieved by utilizing the reciprocating motion of contact member 78 in order to retract the sensor roller 46 of the product sensor positioned in the zone operated by that actuator. Thus, the necessity for solenoids or cylinders to retract the sensor is completely avoided. Furthermore, the selective mounting of valve 62 to either vertical wall 100 of stationary support member 64 or to vertically reciprocating member 102 of contact member 78 allows particular additional product sensors 42 to be of the non-retractable type. Such additional non-retractable sensor located at various positions along the accumulation conveyor provides a guardian control to reduce the build-up of product on actuated zones resulting from a failure of one of product sensors. It may additionally be desirable to have non-retractable sensors to provide singulation between adjacent packages. The separate functions performed by retractable and non-retractable sensors are readily accomplished without requiring different sensor hardware. In other words, all of the physical components are the same whether a retractable product sensor is provided, as illustrated in Figs. 12 and 14, or an additional non-retractable guardian-type product sensor is provided, as illustrated in Figs. 13 and 15. Thus, it is preferably the selective mounting of valve 62 to either vertical wall 100 or vertical member 102 which determines the retractable or non-retractable sensor configuration. With an accumulation conveyor, it is sometimes desirable to apply a brake to rollers that are not being driven in order to maintain proper positioning between adjacent packages by avoiding package creep. This may be accomplished, as the preferred embodiment of Fig. 20 exemplifies, by the utilization of a brake assembly 112 defined by the same major components making up actuator 38. Thus, brake assembly 112 and actuator 38 are both control devices made from common components. However, brake assembly 112 is mounted to the side rail 26' opposite the side rail to which actuators 38 are mounted and is positioned directly below rollers 30 rather than below upper portion 40 of drive belt 36. Furthermore, contact member 78' is covered by a high-friction material 114. When a pneumatic fluid is applied to the diaphragm 74' of brake assembly 112, its contact member 78' will reciprocate upwardly bringing high-friction surface 114 into direct engagement with rollers 30. Because high-friction surface 114 does not move with respect to contact member 78', this actuation of brake assembly 112 will cause rollers 30 adjacent brake assembly 112 to be retained against rotation. Of course, as would be understood by those skilled in the art, brake assembly 112 would only be actuated when the actuator 38 operating the same rollers is not being actuated. In the illustrated embodiment, there is preferably no valve 62 associated with brake assembly 112. Preferred embodiments of the present invention are capable of providing a fine degree of control over product on accumulation conveyor 25. Indeed, in a preferred embodiment, each zone "A", "B", . . ., "N" may be the longitudinal length of each individual contact member 78, which is approximately 305 mm (12 inches). In order to further facilitate such a fine degree of control over the conveyed product, accumulation conveyor 25 may include a discharge conveying section 116 which, in the illustrated embodiment, includes two or more rollers 30' interconnected by flexible bands 118 (Figs. 21 and 22). Discharge conveying section 116 is driven, when it is desired to discharge packages from accumulation conveyor 25, from upper portion 40 of drive belt 36. Upper portion 40 is brought into driving engagement with discharge conveying section 116 by a pulley 120, which is the return sheave for drive belt 36. Pulley 120, which is the width of drive belt 36, is mounted by an eccentric 122 to a stub shaft 124 attached to side rail 26. A control device, such as a pneumatic cylinder 126, is connected with eccentric 122 at one end and at an opposite end 128 to side member 26. For example, when cylinder 126 is extended, as seen in Fig. 21, it rotates eccentric 122 clockwise about shaft 124 in order to lower pulley 120. When cylinder 126 is retracted, as seen in Fig. 22, it rotates eccentric 122 counter-clockwise about shaft 124 in order to raise pulley 120 upwardly. The elevation of pulley 120 brings drive belt 36 into direct driving engagement with discharge conveying section 116 and, thereby, drives rollers 60' in order to discharge packages from accumulation conveyor 25. In a preferred embodiment, a brake assembly 112 will be positioned laterally of pulley 120 below discharge conveying section 116 in order to brake rollers 30' when it is desired to not discharge packages from accumulation conveyor 25. Thus, in order to discharge product from accumulation conveyor 25, cylinder 126 will be retracted in order to rotate eccentric 122 about shaft 124 in order to bring pulley 120 and, hence, drive belt 36 into driving engagement with discharge conveying section 116, while the brake assembly will be deactuated. When it is desired to not discharge product from the accumulation conveyor, cylinder 126 will be extended in order to retract pulley 120 and, hence, drive belt 36 from discharge conveying section 116, and the brake assembly will be actuated to brake the rollers. Drive belt 36 is preferably driven by a drive assembly, generally illustrated at 128, which is supported by side rails 26 of conveyor 25 (Figs. 23-25). The drive assembly includes a frame defined by a pair of side members 130 and a pair of end members 132. Drive assembly 128 includes a drive pulley 134 driven through a gear reducer 136 by an electric motor 138. Gear reducer 136 and motor 138, which define a motor assembly, are mounted to a cross member 28. Drive assembly 128 further includes a guide pulley 155 and a take-up assembly 140 in order to remove slack from drive belt 36. Take-up assembly 140 includes a take-up pulley 142, which is biased to the left, as viewed in Fig. 23, by a pneumatic take-up cylinder 144 connected with side member 130. Take-up assembly 140 additionally includes a slidable mount 146 in order to slidably mount take-up pulley 142. Slidable mount 146 includes a pair of ball slides 148 mounted to side members 130 and a base member 158 for slidably supporting take-up pulley 142 on the ball slides 148. Because drive assembly 128 may be supported substantially exclusively from frame members 26, the drive assembly can be positioned, theoretically, anywhere along the length of accumulation conveyor 25. Fig. 24 illustrates the positioning of drive assembly 128 adjacent the product intake portion 152 of accumulation conveyor 25. In such configuration, the drive belt 36 extends directly from drive pulley 134 to drive belt idler pulley 156 at the product intake portion. Drive assembly 128 may additionally be applied to an intermediate portion 158 between intake portion 152 and discharge section 116, as illustrated in Fig. 25. When applied to intermediate portion 158, additional guide pulleys 154 are mounted to side member 26 in order to elevate the portion of drive belt 36 between drive assembly 128 and idler pulley 156. However, it can be seen that drive assembly 128 is otherwise identical between Fig. 24, in which it is applied adjacent intake portion 152, and Fig. 25, in which it is applied at an intermediate portion anywhere along accumulation conveyor 25. Not only does this provide exceptional flexibility in the layout of the accumulation conveyor assembly, it also eliminates the necessity for maintaining an inventory of drive assembly units of various configurations. It is contemplated that drive assembly 128 may be readily removed and replaced with minimal downtime to accumulation conveyor 25. In order to provide a sensing area that is longer than the width of sensing roller 46, additional sensing rollers may be installed. In this case, levers 58 of adjacent product sensors 42 may be mechanically combined with a connecting rod 160 (Figs. 26 and 27). In this manner, a product deflecting one sensing roller 46' will actuate the combined sensor assemblies. Support member 64 of actuator 38 includes an opening 162 through which connecting rod 160 may pass. Figs. 28 and 29 illustrate an embodiment of an accumulation conveyor 25' in which the rollers 30'' are too closely spaced, such as on 50.8 mm (two-inch) centers, to accommodate a separate sensing roller. Accumulation conveyor 25' includes a product sensor 42'' having a sensor roller 46'' which also is a load-bearing roller. Sensing roller 46'' is mounted to a sensor arm 44'' that pivots about a shaft 52' of adjacent roller 30''. Sensor arm 44'' includes an actuating surface 60' in order to selectively actuate valve 62. Sensing roller 46'' rotates downwardly in response to a package "Y" acting against the bias of a spring (not shown). Sensing roller 46'' may be retracted by the actuation of actuator 38'' if valve 62 is mounted for vertical reciprocal movement with contact member 78'', in the manner previously set forth. Preferably, the drive belt 36 is a low-stretch belt having a high-friction face and a low-friction backing. Such belt may be reinforced with Kevlar aramid fibers. The high-friction face may be a nitrile-butadiene rubber (NBR) material. The low-friction backing may be a nylon fabric backing. In the illustrated embodiment, the belt is marketed by Habasit, located in Switzerland, under Model No. XVR-1317R. High-friction member 114 can be made from a high-friction material, such as PVC or NBR. The support member 64, contact member 78 and pneumatic block 84 can be molded from an acetal material, such as Delrin manufactured by DuPont Polymers Corporation. Preferred embodiments in accordance with the present invention are exceptionally flexible in application. For example, by reference to Fig. 11, multiple actuators 38 and slave actuators 38' may be pneumatically actuated concurrently by the use of a pneumatic block 84' to inflate the diaphragms of slave actuators 38' from an adjacent actuator rather than from a valve 62. In this manner, an accumulation conveyor may be provided in which each zone is larger than a single actuator 38. Each pneumatic block 84' includes terminals 92 for engagement with the diaphragm 74 of actuators 38' but does not include a terminal for interfacing with a valve. Although the illustrated embodiments use a sensing roller product sensor, accumulation conveyors utilizing other sensors, such as photodetectors and other pneumatic sensors, may be used. Although the illustrated embodiments use a drive belt, padded chain drive members and other continuous drive members such as drive-shaft driven line-shaft conveyors and the like may be used. Although the illustrated embodiments use pneumatically actuated conveyors, accumulation conveyors that are hydraulically or electrically actuated may be used. Other changes and modifications in the specifically described embodiment can be carried out without departing from the scope of the invention claimed.

Claims: An accumulation conveyor comprising: a plurality of product conveyors arranged in tandem and each including a product conveying surface and being responsive to an actuator (38,38',38'') in order to convey product in a given direction on said product conveying surface; a product sensor (44,46,62; 44',46',62; 44'',46'',62) positioned along said accumulation conveyor at a particular one of said product conveyors for sensing the presence of product at said particular one of said product conveyors and for causing actuation of a product conveyor upstream thereof with respect to product movement along said accumulation conveyor; characterised by a said actuator (38,38',38'') for said particular one of said product conveyors being mechanically coupled with said product sensor wherein said actuator, in response to another downstream product sensor, retracts said product sensor from the path of movement of product along said accumulation conveyor concurrently with actuation of said particular one of said product conveyors. An accumulation conveyor as claimed in Claim 1 wherein said actuator has a reciprocating member (78) that reciprocates toward the conveying surface of said particular one of said product conveyors to actuate said particular one of said product conveyors and wherein said product sensor (104) is mechanically coupled with said reciprocating member (78) to retract said product sensor from the path of movement of product along said accumulation conveyor. An accumulation conveyor as claimed in Claim 1 or Claim 2 wherein said product sensor includes a sensing member (46,46',46'') in the path of movement of product on said particular one of said product conveyors and a fluid valve (62) operated by movement of the sensing member in response to product contacting said sensing member. An accumulation conveyor as claimed in Claim 3 wherein a force-producing connection between said actuator and said product sensor includes said fluid valve (62) being in a line of force between said actuator and said product sensor. An accumulator conveyor as claimed in Claim 3 or Claim 4 in which said fluid valve (62) is mounted to said reciprocating member. An accumulation conveyor as claimed in Claim 1 in which each of said product conveyors includes a multiplicity of conveying rollers (40) for supporting product and being rotatable for conveying said product and defining said conveying surface, said rollers being grouped in tandem zones (A, B, C ... N); each of said zones corresponding to one of said product conveyors; a mechanical drive member (114) that may be selectively applied to at least one of said zones in order to rotate the rollers in that zone to drive product; wherein said actuator (38,38',38'') in each of said zones selectively applies said drive member to that zone; wherein said product sensor (46,46',46'') in each of said zones is operatively connected with each said actuator for sensing product in the vicinity of the zone operated by the connected actuator when said product sensor is extended to a sensing position, each said product sensor being physically located in a zone downstream of the zone operated by the connected actuator in the direction of product movement along said conveying surface; particular ones of said actuators being mechanically coupled with the product sensor located in the zone operated by that actuator in order to establish said force-producing connection to retract the mechanically coupled product sensor to a retracted position in response to applying said drive member to the zone operated by that actuator; and wherein an actuator is applying said drive member to the zone operated by that actuator if the product sensor operatively connected with that actuator is being retracted by said force-producing connection from one of said particular ones of said actuators or if the product sensor operatively connected with that actuator is extended to a sensing position and not sensing the presence of a product. An accumulation conveyor as claimed in Claim 6 wherein said product sensor includes a sensing roller (46,46',46'') and a fluid valve (62) actuated by said sensing roller and wherein said mechanical coupling is said fluid valve being mounted to said actuator and juxtaposed with said sensing roller. An accumulation conveyor as claimed in Claim 6 or Claim 7 wherein each of said actuators includes a fluid-actuated diaphragm that is connected with the product sensor operatively connected with that actuator. An accumulation conveyor as claimed in Claim 6 or Claim 7 or Claim 8 wherein other ones of said actuators are not mechanically coupled with the product sensor located in the zones operated by said other actuator. An accumulation conveyor as claimed in claim 1 in which each product sensor includes an arm (44,44'',46,46'') that is selectively positioned in the path of product being conveyed by the product conveyors; and in which a force-producing connection (78,106,62,102) is provided from said actuator (38,38',38'') for said particular one of said product conveyors to said product sensor wherein said force-producing connection applies force to said product sensor arm to retract said product sensor from the path of movement of product along said accumulation conveyor concurrently with actuation of said particular one of said product conveyors. An accumulation conveyor as claimed in claim 10 wherein each of the product sensors includes a switch (62) having an actuation member (104) juxtaposed with said arm, wherein the force-producing connection includes said switch being in a line of force between actuator of said downstream conveyor and said arm to operate said switch to one state when moving said arm to a retracted position to retract said product sensor, whereby product causes said arm to operate said switch to another state when said arm is positioned in the path of product being conveyed; and a control (84,84') that is responsive to the states of said product sensor switches in order to selectively actuate said product conveyors in a manner that provides for selective accumulation of product on said product conveyors. An accumulation conveyor as claimed in claim 11 wherein said control is pneumatic. An accumulation conveyor as claimed in any one of Claims 1 to 12 in which a force-producing connection from said actuator for said particular one of said product conveyors to said product sensor uses the mechanical movement of the actuator of the zone in which the product sensor is physically located in order to effect the retraction of the product sensor. An accumulation conveyor as claimed in Claim 1 which has a pair of spaced-apart support rails (26,26'), a multiplicity of rollers (30) defining the product conveying surfaces of the product conveyors, an endless drive member (36) juxtaposed with the rollers, a drive motor (138) for driving the drive member, a plurality of said product sensors (42) positioned along the conveying surfaces for detecting the presence of product at positions spaced along the conveying surfaces, the actuators (38,38') being positioned along the conveying surfaces adjacent the drive member (36) for selective reciprocal movement of the drive member into driving engagement with particular rollers adjacent particular actuators, each of the product sensors having an elongated sensing member (46,46') selectively in the path of movement of product on the conveyor and a counterweight (48), the difference in weight between the counterweight and sensing member biasing the sensing member upwardly into the path of movement of product, the counterweight including at least one weight member (56) and an elongated spacer (54), the spacer being approximately the same weight as the sensing member, whereby the difference in weight is established by the weight member. An accumulation conveyor as claimed in Claim 14 in which the weight member (56) comprises a pair of members separated by the spacer. An accumulation conveyor as claimed in Claim 14 or Claim 15 in which the spacer (54) has approximately the same weight per unit length as the sensing member. An accumulation conveyor as claimed in any one of Claims 14 to 16 in which the spacer (54) is non-rotatably mounted. A method of selectively conveying and accumulating product which includes using an accumulation conveyor as claimed in any one of the preceding claims. A method of selectively conveying and accumulating product including: providing a plurality of product conveyors arranged in tandem and each including a product conveying surface; providing retractable product sensors (42,42'') along the product conveying surfaces for sensing the presence of product when not retracted; providing actuators (38,38',38'') for causing each of the product conveying surfaces to convey product; causing motion in one of the actuators to actuate the associated product conveyor and thereby convey product with the associated conveying surface; characterised by mechanically coupling the actuator for a particular conveyor to a said product sensor which is located at the particular conveyor, the said motion of the actuator for the particular conveyor, in response to another downstream product sensor, retracting the coupled product sensor from the path of movement of product along the accumulation conveyor concurrently with actuation of said particular one of said product conveyors. A method as claimed in Claim 19 which includes positioning said coupled product sensor juxtaposed with said one of the actuators. A method as claimed in Claim 19 or Claim 20 which includes attaching a portion of said coupled product sensor to said one of said actuators. A method as claimed in any one of Claims 19 to 21 in which said providing product sensors includes providing sensing members responsive to the presence of product and switching members selectively actuatable by said sensing members.

Inventors: BAKKILA DOUGLAS J, COTTER DAVID H, DEMAN SAMUEL J, SCHIESSER RICARDO N, TERPSTRA ARTHUR J JR, WOLTJER BERNARD H, BAKKILA, DOUGLAS J., COTTER, DAVID H., DEMAN, SAMUEL J., SCHIESSER, RICARDO N., TERPSTRA, ARTHUR J., JR., WOLTJER, BERNARD H.
Applicants: MANNESMANN DEMATIC RAPISTAN CO, MANNESMANN DEMATIC RAPISTAN CORP.
Application year: 1994
Main classification: B65G47
IPC codes: B65G47